Currently, there are several different methods for extruding an aqueous solution containing cellulose and a water soluble solvent into cellulose fibers. Each of these methods utilizes special equipment to heat the aqueous solution and extrude it through a die block assembly. The die block assembly can include various components for directing and distributing the aqueous solution and pressurized gas through a plurality of nozzles to form a plurality of molten filaments. The aqueous solution is usually extruded in a downward direction such that the pressurized gas and gravity will cause the aqueous solution to attenuate into a plurality of molten filaments. The molten filaments are then contacted with a liquid which causes a major portion of the solvent to solvate into the liquid solution and thus allows the molten filaments to coagulate into solid cellulose fibers. These solid cellulose fibers are then collected on a moving surface, such as a porous conveyor belt or rotatable drum and form a non-woven web.
Up until now, no one has been able to design and construct an apparatus or process which will allow cellulose fibers having a diameter of less than about 15 microns to be extruded and formed at a throughput that would make such a process economically feasible. In addition, no one has been able to design and construct a spinnerette that extrudes 20 or more molten filaments per linear centimeter at a throughput of greater than 0.1 grams/hole/minute at a production speed of up to about 750 meters per minute. Furthermore, no one has been able extrude an aqueous solution containing cellulose and a solvent at back pressures of more than 20 bar without damaging the spinnerette. Still further, no one to date has been able to extrude and form very fine cellulose fibers having a diameter of less than 5 micron at a throughput of greater than 0.5 grams/hole/minute at a production speed of up to about 750 meters per minute. Lastly, no one to date has been able to form a non-woven web constructed from such cellulose fibers which has a basis weight of less than about 1 gram per square meter at a production rate of more than about 30 meters per minute.
Now an apparatus has been invented which will allow one to extrude and form cellulose fibers each having a diameter of less than about 15 microns at a throughput of greater than about 0.1 grams/hole/minute. The apparatus is also capable of forming very fine cellulose fibers each having a diameter of less than about 5 microns at a throughput of greater than about 0.5 grams/hole/minute. Furthermore, the apparatus produces cellulose fibers having unique characteristics that can be collected to form a non-woven web.